Electric primary cell



Aug. 4, 1936. c. J. GORDON ELECTRIC PRIMARY CELL Filed April 5, 1954 2Sheets-Sheet 1 1936- c. J. GORDON ELECTRIC PRIMARY CELL 'Filed April :5,19:54 2 Sheets-Sheet 2 Fig. 10

Fig. 11.

HA5 HTZ'OR/VEYQ Patented Aug. 4, 1936 Christian Jensen Gordon, London,England Application April 3, 1934, Serial No. 718,769 In Great BritainApril 6, 1933 16 Claims.

The object of this invention is to provide an improved primary cell ofthe kind in which magnesium is the electropositive electrode. Within theterm magnesium, it is intended to include appropriate alloys in whichmagnesium is the predominating material. For such alloys to be suitable,it is necessary that the metals added to the magnesium should not beplaced very far away from magnesium in the electro-chemical series- Asan example of an alloy which is appropriate, one containing about 7% ofaluminium and from 1-2% of manganese and the remainder magnesium may bementioned. The addition of aluminium within the range of 2-7 has beenfound to be an improvement on commercially pure magnesium. Where theword magnesium is .used in the following specification and claims(unless the context indicates otherwise), it is to be assumed that itincludes suitable alloys as well as substantially pure magnesium.

The invention relates to primary cells having a layer of fibrousmaterial lying between and in contact with the magnesium electrode andthe second electrode and serving as a carrier for the.

electrolyte.

The invention deals with the nature, form and disposition of theelectrodes and the fibrous layer when assembled in their appropriaterelationship for use in a cell. of the electrolyte. Electrolytessuitable for cells embodying the present invention are described in andform the subject of my continuation in part application Serial No.42,039;

In accordance with the invention one of the electrodes is made of carbonof an open structure that is, porous or granular or powdered carbon,which is in contact with air on one or more of its surfaces, so that aircan pass through the pores or spaces in the electrode material itself tothe layer of fibrous material which is in contact with it.

The air is caused by the action of the fibrous layer to effect thedepolarization. The full theory of this action is not understood but itappears evident that it is the oxygen in theair which is essential forthe depolarizing and that it can be conveyed along the layer to theplace where depolarization occurs. Where granular or powdered carbon isused, it must be carried on a suit able conducting support or heldwithin a metal container which forms the outer part of the cell. Theconducting support may be a metal gauze or a woven fabric made of amixture of thread, such as cotton, with wire. In each case, the carbonpowder can be made to adhere to its support by being pressed into themeshes thereof and on its It does not deal with the nature magnesiumelectrode to the other.

surface. In the case of a porous solid carbon body or of a wovenmaterial serving as a support for carbon powder, the electrode may bemade as thewall of the cell and may have one surface in contact with theelectrolyte and the opposite surface exposed to the air. In the case .ofpowdered or granular carbon-held in a solid metal container, only theend surface or surfaces can be exposed.

For the fibrous layer, material of open texture is used. Many fibres aresuitable but have somewhat varying degrees of effectiveness. It ispreferred to use cellulose fibres, such as Wood ,wool, or blottingpaper. This material is inert and readily obtainable and has been foundto be particularly effective for the purposes in view.

In orden to avoid cutting oif air from the fibrous layer, theelectrolyte must be fed to the fibrous material without immersion of anyimportant part of the area of the electrodes. The supply of theelectrolyte, in accordance. with this condition, can be effected byplacing the fibrous body in contact with a body of solidified materialwhich is housed in an appropriate part of the container of the cell andis dissolved by the addition of water. By regulating the supply ofwater, some control of the action of the cell can be exercised. This isof importance in this type of cell since a slight chemical action on themagnesium electrode proceeds continuously while it is in contact withwater and air.

It appears that, in this type of cell, it is'the reaction between thewater and the magnesium which provides the E. M. F. of the cell. Theelectrolyte serves the purpose of providing a conductive path betweenthe electrodes.

The method of supplying electrolyte above described has the advantagethat the electrolyte may be fed progressively from one end of the Thisis of importance because, as the result of the action between the waterand the magnesium electrode, a comparatively large body of anon-conducting or poorly conducting compound is produced. By arrangingthe feed of the electrolyte to take place from the end of the electroderemote from the terminal, it can be ensured that the absorption of theelectrode proceeds progressively from the inner end to the terminal endand accordingly this means compensates approximately for the increasedue to other causes so that the internal resistance of the cell remainsapproximately constant, at least until the latest stage of the life ofthe cell is reached.

Since the action of the water on the magnesium during the life of thecell produces a substantial increase in the volume of the contents ofthe cell, it is important to provide for expansion within the cell toprevent the fibrous layer from being compressed too heavily. Suchcompression would render the layer incapable of carrying out properlyits function of holding electrolyte and its function of bringing aboutdepolarization. Room for expansion may be provided by making the cellwith concentric electrodes and with the outer electrode expansible orthe inner electrode collapsible or with both of these.

The invention will be further described in connection with two examplesof cells embodying it, which are shown in the accompanying drawings.

Figures 1-4 show a type of cell suitable for comparatively light serviceand comprising three units connected in series.

Figure 1 is a vertical section on the line IV-'-IV of Figure 2.

Figure 2 is a horizontal section on the line VV of Figure 1.

Figure 3 is a side elevation of three groups of electrodes, one of thesebeing shown in section, and Figure 4 is a side elevation of thecontainer partly in section.

Figures 5 and 6 show in end elevation and side elevation analternativeform of magnesium electrode suitable for use in cells asshown in Figures Figures 'l and 8 show in end and side elevationrespectively another form of such an electrode.

Figure 9 corresponds to Figure 1 but includes an alternative form ofouter electrode.

Figures 10 and 11 show developed views of alternative parts of the outerelectrode included. in Figure 9.

Figure 12, which also corresponds to Figure 1, includes a furtheralternative form of outer electrode.

The type of cell in the drawings is intended for a comparatively smallcurrent; for instance, the current may be of the order 20 milliamperes.The surface of magnesium per amp. is of the order of 100 square inches(640 square centimeters). The open circuit voltage is about 1.3.

In cells of the kind shown, the magnesium I electrode 22 is placed inthe centre of the cell and is in the form of a cylindrical rod withlongitudinal flutes on the surface so as to increase the area. It has aterminal screw 23 at the upper end. The central rod is surrounded by alayer of fibrous material 24 formed by coiling a strip of wood wool intothe form of a tube. Outside and in contact with this layer, is thesecond electrode 25. This is of porous carbon made in two half cylinderswith longitudinal flutes on both the inner and the outer surface. Thesetwo halves are held together by a rubber'band 46.

From the two halves of the electrode 25, connec-' tions 26 are takenoff. It will be seen from Figure 3 that, by means of these connectionsand the terminal screws 23, the three cells are connected in series andar also connected with the aid of an additional'wire 21 to terminals 28mounted on the top plate 29 of the-battery. This plate 29 and the casing30 are made of insulating material. They are connected together byscrews 3|. The casing 30 is divided panied by eXpansion.

into three chambers and each chamber is in communication with theexterior air by means of holes 32 which provide that the exteriorsurfaces of the carbon electrodes 25 are in contact with air.

e Near the lower end of the casing 30, is a partition 33 which separatesthe three chambers which contain the electrodes from three smallerchambers 34 in each of which is placed a pad 35 containing electrolytematerial. Communication is provided between the upper and lower chambersby way of an aperture in the partition 33 through which passes fibrousmaterial 36 which is spread out above and below the partition and servesto establish communication between the pad 35 and the fibrous layer 24.The chamber 34 is closed by a cup 31 which can be removed to receive thepad 35.

When the cell is complete it can be put into action by supplying waterto the pad and the fibrous material. This can readily be done byremoving the cup 31, filling with water and replacing it. The fibrousmaterial 3'6 is then in contact with the water and feeds it to the layer24. The cell will now remain active until substantially the whole of thewater has been used up. Each pad of electrolyte material will generallysufiice for several fillings with water and will generally be sodesigned that it will be exhausted in about the same time as themagnesium electrode is used up.

The chemical transformation of the magnesium will proceed from thebottom upwards in such a way as to leave the electrical connections(both electrolytic and otherwise) complete in the upper part of thebattery.

The chemical change will in general be accom- This can be accommodatedby the split construction of the carbon electrodes, the two halves ofwhich can move apart commencing at the lower end as the action proceeds.Alternatively or in addition increase in volume may be provided by thecollapse of the magnesium electrode, For this purpose it can be made asa hollow rod, preferably in a form which favours inward collapse. Anexample is shown in Figures 5 and 6 where the electrode is an oval tubewith comparatively thin walls.

As an alternative to the arrangement described. the supply of water maybe effected through apertures in the top plate 29 and for this purposeit is preferable to use magnesium electrodes of tubular form with radialperforations through which the water can flow outwards t0 the fibrouslayer 24. An example of such an electrode is shown in Figures 7 and 8.In this example the electrode 22 has a central circular bore 38 whichcommunicates with the exterior through a large number of perforations39.

The solid carbon electrode shown in Figures 1, 2' and 3 may be replacedby a granular carbon electrode as shown in Figure 9 or by a powderedcarbon electrode as shown in Figure 12. The

general construction of this cell is similar to that just described andcorresponding parts are indicated by the same reference letters inFigure 1 and Figure 9.' The carbon granules 40 are enclosed in a tube 4|which may be either of the construction shown in Figure 10 or that shownin Figure 11. In Figure 10, the tube 4| is formed from a strip of coppergauze which is shown there as afiat strip as it is prepared with aterminal wire 42 ready for being bent into cylindrical form forinsertion in the container 30. The

electrode 22 is held in place by its terminal screw 23 which passesthrough a cover plate 43. This plate has a second hole through whichpasses the The tube 48 may alternatively be formed of a strip of cottonfabric 44 (Figure 11) through which are passed a number of wires 45which are twisted together to form the terminal connection 42. Thesewires serve as electrical connection to the carbon and also givesufficient stiffness to the fabric 44.

Figure 12 shows an arrangement similar to that of Figure 9 with theexception that the outer electrode is formed from carbon powder I40carried by a tube of copper gauze 4| which is similar to the tube shownin Figure 9 and described in connection with Figure 10. The carbonpowder is caused to adhere to the gauze by pressure assisted by abinding agent. This may be a tarry body from which volatile parts can bedriven oif by heat after the attachment of the carbon powder to thegauze has been effected, thereby leaving a residue consisting only ofcarbon.

It will be recognized from the preceding description that this type ofcell is inert until water is added and becomes inert again when thewater has been used up and can then be brought again into activity bythe addition of a further supply of water. Throughout its active life,the cell has a practically constant open circuit voltage. It can beshort-circuited without permanent injury and with no other effect thanan increased consumption of the magnesium electrode. Polarization isnegligible under proper working conditions and even aftershort-circuiting normal conditions are very rapidly restored.

The construction of these cells is suchas to facilitate the use ofelectrolyte material in a solid form, that is to say, in a form whichcan be handled in one piece per cell and placed in position as a padsufiicing for a complete working charge.

The chemical compound formed by the action in the cell is not depositedon the surface of the magnesium electrode and therefore does not hinderthe flow of current.

What I claim is:-

1. A primary cell of the type having its electromotive-force generatedby the action of water on magnesium comprising an electrode ofmagnesimn, a second electrode of carbon of open structure exposed to airand a layer of fibrous material of open texture lying between and incontact with the two electrodes and exposed to air through the carbonelectrode and serving as a carrier for the electrolyte and for air fordepolarizing.

2. A primary cell comprising an electrode of,

magnesium, a second electrode" of carbon of open structure exposed toair, terminal connections located at one end of the electrodes, a bodyof electrolyte material separate from the electrodes and locatedadjacent to the end of the electrodes remote from the terminals, a layerof fibrous material of open texture lying between and in contact withboth electrodes and with the electrolyte material and exposed to airthrough the carbon electrode and serving as a carrier for theelectrolyte and for air for depolarizing.

3. A primary cell of the type having its electromotive force generatedby the action of water on magnesium, comprising an electrode ofmagnesium, a second electrode of finely divided carbon exposed to airand forming a non-self-sup porting structure, a. conductive membersupporting the second electrode, and a layer of fibrous material of opentexture lying between and in contact with the two electrodes exposed toair through the carbon electrode and serving as a. carrier for anelectrolytaand for air for depolarizing.

4. A primary cell having an electrode of magnesium, a second electrodeof finely divided carbon exposed to air, a conductive support for thesecond electrode, comprising a woven fabric having conductive wirestherein, and a layer of fibrous material of open texture lyingbetweenand in contact with the two electrodes and exposed to air throughthe carbon electrode and serving as a carrier for an electrolyte and forair for depolarizing.

5. A primary cell having an'electrode of magnesium, a second electrodeof finely divided carbon exposedto air a wire gauze conductive supportfor the second electrode and a layer of fibrous material of' opentexture lying between and in contact with the two electrodes and exposedto air through the carbon electrode and serving as a carrier 'for anelectrolyte and for air for depolarizing.

6. A primary cell having an electrode of magnesium, a secondelectrcde,-a layer of fibrous material of open texture lying between andin contact with the two electrodes and serving as a carrierfor theelectrolyte and for air for depolarizing and a metal container for theelectrodes and fibrous material, the second electrode being formed offinely divided carbon disposed between the wall of the container and thefibrous layer and exposed to air and the fibrous layer being exposed toair through the carbon electrode.

7. A primary cell comprising a central electrode of magnesium, anelectrode of carbon of open structure surrounding the central electrodeand exposed to air, a layer of fibrous material of open textureinterposed between the two electrodes and lying in contact with both ofthem and exposed to the air through the carbon electrode and serving tocarry electrolyte and air for open structure and surrounding the centralelectrode and exposed to air, and a fibrous layer of open textureinterposed between the two electrodes and exposed to air through thecarbon electrode and serving to carry electrolyte and air fordepolarizing.

9. A primary cell comprising a central collapsible. tubular electrode ofnon-circular, crosssection made of magnesium, an electrode of carbon ofopen structure surrounding the central electrode and exposed to air, anda layer 01. fibrous material of open texture interposed between the twoelectrodes and lying in contact with both of them and exposed to airthrough the carbon" electrode and serving as a carrier for electrolyteand for air for depolarizing.

10. A primary cell comprising a' central tubular and perforatedelectrode of magnesium, an electrode of carbon of open structuresurrounding the central electrode and exposed to air and a layer offibrous material of open texture interposed between the two electrodesand lying in contact with both of them and exposed to air through thecarbon electrode and serving to carry electrolyte and air fordepolarizing.

11. A primary cell comprising an electrode 01' magnesium, a secondelectrode, terminal connections located at one end of said electrodes, alayer of fibrous material of open texture lying between and in contactwith the electrodes and exposed to air and means for feeding electrolyteto said layer at the end remote from the terminals. 7 v

12. A primary cell comprising a central electrode of magnesium, anoutwardly expansible tubular electrode of carbon of open structuresurrounding the central electrode and exposed to air and permittingincrease of the volume enclosed between the two electrodes, a fibrouslayer of open texture interposed between the two electrodes and exposedto air through the carbon electrode and serving to carry electrolyte andair for depolarizing.

13. A primary cell comprising a central inwardly collapsible tubularelectrode of magnesium, an electrode of carbon of open structuresurrounding the central electrode and exposed to air, and a fibrouslayer of open texture interposed betweenthe two electrodes and exposedto air through the carbon electrode and serving to carry electrolyte andair for depolarizing.

14. A primary cell comprising a central electrode of magnesium, anelectrode of carbon of open structure surrounding the central electrodeand exposed to air, and a layer of fibrous material of open texturelying between and in contact with both electrodes and exposed to airthrough the carbon electrode and serving to carry electrolyte and airfor depolarizing, an insulating casing pervious to air enclosing thewhole, a chamber in the base of the casing, a partition, separating thechamber in the base from the remainder of the casing, the said partitionhaving an aperture through which passes the fibrous material.

15. A primary cell comprising a central electrode of magnesium, anoutwardly movable electrode surrounding the said magnesium electrode andpermitting increase in volume of the space between the two electrodes,and a layer of fibrous material of open texture lying between and incontact with the electrodes and exposed to air and serving as a carrierfor the electrolyte and for air for depolarizing.

16. A primary cell comprising a central tubular inwardly collapsibleelectrode of magnesium, an outer electrode surrounding the saidmagnesium electrode and a. layer of fibrous material of open texturebetween and in contact with the electrodes and exposed to air andserving as a carrier for electrolyte and for air for depolarizing.

CHRISTIAN JENSEN GORDON.

